Cap for armor-piercing projectiles



ROBERTVABBOTT HAIDFIELD, or WESTMINSTER, ENGLAND.

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No Drawing.

To all whom it may concern:

Be it known that 1, Sir ROBERT ABBOTT HADFIELD, baronet, F. R. 5., a subject of the King of Great Britain and Ireland, residing at Vestminster, England, have'invented Improvements in or Relating to Caps for Armor-Piercing Projectiles, of which the following is a specification.

This invention has reference to that kind of caps of Conical, conoidal or like shape,

for use with armor piercing projectiles, that are made of metal or alloy, such for example as nickel chromium steel, that is capable of being stiffened or hardened and possesses considerable toughness or strength,'and the forward end portions of which that will be in front of the point of the projectiles to which such caps are fitted, are made of varying degrees of stiffness or hardness, as described in the specification of Letters Patent No. 1,310,076 with the object of enabling the capped projectile to pass through an armor plate, under varying conditions of impact, without being broken. up, or broken up to such an extent as would impair its subsequent proper action.

The present invention has for object to facilitate the manufacture of such caps in a regular and reliable manner so that they shall better fulfil, in a satisfactory manner, the functions which such caps are required to fulfil in practice.

For this purpose a cap made of steel of the kind referred to, after being forged or otherwis formed approximately to the required finished shape, is subjected to the special heat treatment hereinafter described comprising successive heatings and coolmgs whereby the condition of the steel of which it is made is improved and a special graduated stifiness or hardness is imparted to the This special heat treatment consists in heating the cap to a high temperature in a furnace, then rapidly cooling it by complete immersion in a cooling medium, such as water or oil, and then gradually withdrawing it, either continuously or in steps or stages, in such a manner that when completely withdrawn it will be at a temperature well below the temperature corresponding to the recalescence point of the steel used but still sufficiently high to evaporate water placed in its interior, the

Specification of Letters Patent. Patented A1313 1.9, 1921 Application'filed May 22, 1920. Serial No. 383,605.

cap being finally cooled slowly to the ordinary temperature of the atmosphere. It 1s thenreheated in a furnace to ahigh temperature but below that to which it was previously heated, then allowed to cool to some extent, again reheated but to a lower temperature than on first reheating, and finally maximum temperature, by complete immers1on in a cooling medium, such as mentioned. The cap is then finished to shape. The

then heatedto a high temperature and the whole cap then dipped, point downward,

into acooling medium, such as water or oil, so as completely to immerse it therein and where it is allowed to remain until practically cold.

A cap made according to the invention may advantageously consist of nickel chromium steelcontaining under .4L% of carbon, about 4% of nickel and about 2% chromium.

Satisfactory results can be attained "with a cap made of nickel chromium steel having the following composition, namely about 35% carbon, about 3.88% nickel and'about again suddenly cooled while still at the forward end or nose portion of the cap is ture corresponding to the recalescence point of the steel used but still sufficiently high to evaporate water placed in its interior, that is to say, a temperature above 0., the cap being finally cooled slowly to the ordinary temperature of the atmosphere. It is then reheated in a furnace until it attains a temperature of about 765 to 785 0., then allowed to cool to about 400 0., and again heated up to 600 0., and then again cooled by complete immersion in water or oil:

After this treatment the cap is finished to shape. The forward end portion of the cap is afterward stiffened or hardened by heatmgthe nose portion thereof to a tempera ture of about 885 to 900 0., as by dipping such nose portion into molten lead, after which: the whole cap is completely immersed perature, then cooling it, "first rapidly and afterward more slowly to about the temperature of the, atmosphere, reheating it to i a high temperature butbelow that to which it was first heated,

allowing it to partly cool, again reheating it but to a lowertemperature than the first reheating, then suddenly cooling it, afterward heating its forward end or :nose toa high temperature and it therefrom, the

then cooling 'thewhole cap by completely immersing it point. downward in a cooling liquid.

2. The herein described treatment of a cap made of steel of the character herein referred to, for use-with an armor piercing projectile, said treatment consisting in heating the cap to a high temperature, then cooling it by complete immersion in a cooling medium and gradually withdrawing withdrawal being :co1npletely effected while it is at a temperature well below the recalescence point of the steel of which it is composed butstill suiiiciently high to evaporate water placed in its interior, then Eallowing it to cool slowly to about the ordinary temperature .of the atmosphere, reheating it to a high temperature but below that to which it waspreviously heated, allowing it'to partly cool, again reheating it to a loweritenipera- V ture than the first ireheating, suddenly co0lingit while at about the maximum temperature to which. it was last reheated, by com- .plete immersion in a. cooling medium, afterward heatingqits forward end or nose to a high temperature and then immersing it completely, point downward,

mosphere,

in a cooling liquid and allowing it to remainthere until it ispraotically cold. 7 V

3. The herein described treatment of a cap made of nickel chromium steel, said treatment consisting in heating the cap, after it has been formed approximately to shape, to ajtemperature of about 830 C, then cooling it by completely immersing it, point downward, in a cooling liquid, then gradually withdrawing it in such a manner that when completely withdrawn it will be at a temperature well below the recalescence point of the steel of which it is composed 1 but above 100 (l, "finally cooling it slowly to about'the ordinary temperature of the at reheating it to a'temperature of about 765 to 785 0., allowing it to cool to about 400. C., reheatingit to a temperature of about 600 C.,;again cooling it by complete immersion in a cooling liquid,'fin-' ishing it to shape, and stittening or hardening its tront end portion by heating the nose portion thereof to a temperature of about 885 to 900 C. and completely immersing thecap point downward, in a cooling liquid and allowing it to remain there until it is practically cold. 1

' rThe herein described process of producing a steel cap having a stiffened or hardened front :end .portion for use with an.,armor p1ercing;pro]ectile, said treatment consisting in heating the cap to a high temperature, then cooling -it, first rapidly to a temperature well below .the recalesccnce point :otth'e steeland afterward more slowly to about the temperature of the atmosphere,

subjecting the cap to subsequent tempering treatment and finally heating the forward end or nose to a high temperature and then cooling the caprby completely immersing it in a cooling liquid.

'Signedlat London in the county of London England this twenty ninth day of April 1920.

ROBERT ABBOTT HADFIELD. 

